The present invention is directed to a method of splitting a continuous fluid stream into two streams of substantially different volumes. In particular, the present invention is directed to a novel metering valve and the use thereof to split a continuous fluid stream into two fluid streams which simultaneously flow from the valve. The invention has particular use in splitting the flow of a continuous condensed distillate stream into a continuous product stream and a separate continuous reflux stream.
In distillation separation, the distillate or low boiling fraction which is obtained from adjacent the top of a distillation column is condensed and the liquid distillate is typically divided into a product stream and a reflux stream for return to the distillation column. The relative amounts of the product and reflux streams are usually determined by the quality of the distillate. Thus, it is often necessary to reflux a major amount of the distillate while drawing off only a small portion of the product to obtain the desired separation of the feed to the distillation column. Conversely, in some instances the desired separation is easy to attain and it is therefor possible to direct most of the condensed distillate to product while refluxing only a small portion of the condensed distillate stream. The distillation process is usually a continuous process run at attained steady state conditions.
In relatively small continuous distillation operations such as on a laboratory or pilot plant scale, the use of separate receivers, pumps and level controls for both the distillate product and reflux streams are not economical. Thus, a metering valve has been utilized to divide the condensed distillate into the separate product and reflux streams. A valve which has been conventionally used is a three-way valve which includes a single inlet port for the condensed distillate stream and two outlet ports, one for directing the distillate to a product stream and the other to the reflux stream. In such valves, however, the product stream and reflux stream are not directed simultaneously from the valve but alternate on a timed sequence in which the valve stays open only for product outlet for a limited period of time and then is opened only for reflux for a set period of time while the other outlet is closed. Accordingly, at one time there will be a stoppage of the flow of distillate either to the product stream or reflux stream. Such stoppage of flow may disrupt downstream operations at least with respect to further purification of product or, importantly, may disrupt the steady state concentrations achieved along the distillation column as reflux is stopped and then injected into the system.
In the processing scheme described above and in other processing schemes where a split flow is required, it may not be useful to split the flow such as with a T-connecting pipe inasmuch as it is often necessary or desirous that one of the split streams be precisely metered and have a substantially lower volume than the other. In such instance, the T-connector would not provide such uneven flow. Further, as seen from the above description, it is sometimes most useful and even necessary that the two split streams flow simultaneously from the valve to not disrupt downstream processing of the streams, thus, rendering the use of a conventional three-way valve as above-described disadvantageous. Accordingly, there is a need to improve the process of splitting a continuous fluid stream into a relatively large volume flow and a substantially smaller volume flow simultaneously.
Similar to the valve of the present invention which is described hereinafter, valves have been provided to remove from a primary fluid flow a secondary or lower volume flow. For example, U.S. Pat. No. 582,507, issued May 11, 1897, discloses a valve used to remove condensate from a steam line and which includes a passage therethrough for the main flow of gas and a valve stem which passes through the main flow and is seated upon a valve seat which contains a passage from the main flow and directed therefrom. When the valve stem is not seated, condensation in the main gas flow passes through the valve seat and away from the valve and main flow of gas.
U.S. Pat. No. 4,281,935, issued Aug. 4, 1981, discloses a similar valve containing an inlet and outlet for a primary fluid flow, a valve stem which passes through the primary flow and is seated on a valve seat which is located directly across the primary flow path relative to the valve stem and extends into the primary flow. The valve seat includes a passage communicating with the primary flow and with a separate inlet/outlet portion of the valve. The valve is disclosed as being primarily useful for injecting a fluid into the primary flow through the passage contained in the valve seat but, conversely, can be used to remove a small portion of the primary flow through the passage in the valve seat.
Neither of the above patents, however, are concerned with continuously metering a secondary flow from a continuous primary flow. Instead, the patents merely seem to be concerned with an on-off flow of the secondary stream to or from a primary flow stream.
Accordingly, an object of the present invention is to provide a process for splitting a continuous flow of fluid into two streams in which the split streams have substantially differing flow volumes without stoppage of flow.
Another object of the present invention is to provide a process for splitting a fluid flow using a metering valve which splits the flow of fluid into two continuous flowing streams of differing volumes.
Still yet another object of the invention is to provide a process for dividing a distillate stream into a product stream and a reflux stream while maintaining continuous flow of distillate, product and reflux.
A further object of the invention is to provide a novel metering valve for splitting a continuous flow of fluid into two continuous split streams of differing volumes without stoppage of flow.